The present invention relates to a fungicidal composition comprising a fungicidally acceptable carrier and/or surface active agent and synergistically effective amounts of
(a) at least one azolopyrimidine of formula I ##STR3## PA1 in which PA1 (b) and at least one fungicidal active ingredient which is capable of inhibiting the melanin biosynthesis in particular in Pyricularia oryzae the causal agent of the rice blast disease. PA1 x is the efficacy in % compared with an untreated control upon treatment with a fungicidal active ingredient A at a dose rate a; PA1 y is the efficacy in % compared with an untreated control upon treatment with a fungicidal active ingredient B at a dose rate b; PA1 EE is the expected efficacy with a combination of fungicidal active ingredients A and B at a dose of a+b, respectively. PA1 R.sup.1 and R.sup.2 together with the interjacent nitrogen atom represent an optionally substituted 6-membered heterocyclic ring, in particular a 4-methylpiperidine ring, or wherein PA1 R.sup.1 represents an alkyl or haloalkyl group, PA1 R.sup.2 represents a hydrogen atom, or PA1 R.sup.1 and R.sup.2 together represents an optionally substituted alkylene group having 3 to 6 carbon atoms in the main chain, in which one CH.sub.2 group may be replaced by O or NH, and PA1 Hal denotes a halogen atom. PA1 R.sup.5 and R.sup.6 each independently represent a hydrogen atom or an optionally substituted alkyl group; PA1 R.sup.7 independently represents a hydrogen atom or an optionally substituted alkyl group PA1 R.sup.8 and R.sup.9 each independently represent a hydrogen atom or an optionally substituted alkyl or alkenyl group; or R.sup.8 and R.sup.9 together may represent an alkylene group; PA1 Y each independently represents a halogen atom or an optionally substituted alkyl or alkenyl group or a cyano or nitro group; PA1 m is 0 or an integer of 1, 2, 3 or 4. PA1 R.sup.9 represents a C.sub.1-8 -alkyl group. PA1 a carrier agent; PA1 at least one azolopyrimidine of formula I, PA1 at least one MBI, in particular a phenoxyamide of formula II, PA1 optionally a foam breaking agent, in particular a mixture of perfluoroalkyphosphonic acids and/or perfluoroalkylphosphinic acids, in particular Defoamer SF or Fluowett PL, which are commercially available from Clariant GmbH.
R.sup.1 and R.sup.2 each independently represent hydrogen or an optionally substituted alkyl, alkenyl, alkynyl, alkadienyl, aryl, heteroaryl, cycloalkyl, bicycloalkyl or heterocyclyl group, or PA2 R.sup.1 and R.sup.2 together with the adjacent nitrogen atom represent an optionally substituted heterocyclic ring, PA2 R.sup.3 represents a hydrogen or a halogen atom or an alkyl group, PA2 R.sup.4 represents hydrogen or an alkyl or aryl group, PA2 L represents a halogen atom or an optionally substituted alkyl or alkoxy group, PA2 A represents N or CR.sup.5, wherein R.sup.5 has the meaning given for R.sup.4, and PA2 n is 0 or an integer between 1 and 5; and PA2 R.sup.1 represents a C.sub.1-6 alkyl, in particular an isopropyl group, a C.sub.1-6 haloalkyl, in particular a 2,2,2-trifluoroethyl or a 1,1,1-trifluoroprop-2-yl group, or a C.sub.3-8 cycloalkyl group, in particular a cyclopentyl or cyclohexyl group and R.sup.2 represents a hydrogen atom or a C.sub.1-6 alkyl group and/or wherein ##STR4## PA2 wherein L.sup.1 represents a halogen atom, preferably flourine or chlorine and L.sup.2 and L.sup.3 each independently represent a hydrogen atom or a halogen atom, preferably fluorine, in particular wherein L.sup.1 represents fluorine, L.sup.2 represents hydrogen and L.sup.3 represents chlorine or wherein L.sup.1 through L.sup.3 represent fluorine and/or wherein
The fungicidal compounds of formula I are known from U.S. Pat. No. 4,567,263 and U.S. Pat. No. 5,593,996.
The class of melanin biosynthesis inhibitors (MBI) are chemical compounds which are capable of diminishing the in-vivo synthesis of melanin by inhibiting any of the reductase and/or dehydratase enzymes which are responsible for converting tetrahydroxynaphthalene into dihydroxynaphthalene. This class of compounds includes the following known compounds: carpropamid, chlobenthiazione, diclocymet, pyroquilon, phthalide, tricyclazole and certain phenoxyamides, which are known for example from EP 0 262 393 and Japanese patent application JP 5-9165-A.
However, there is no hint to combine the compounds of formula I, with a MBI. Moreover, there is no hint that such mixtures can be advantageously be used for controlling rice diseases such as rice blast and rice sheath blight and others.
Surprisingly, a strong synergy between the compounds of formula I and MBIs in field trials was found when these two compounds were in-tank mixed and when the activity of these co-formulations was compared with that of the solo formulations of each active ingredient.
A mixture of fungicides shows synergistic effect if the fungicidal activity of the mixture is larger than the sum of activities of the separately applied compounds. The expected fungicidal activity for a given mixture of two fungicides can also be calculated as follows (See Colby, S. R., "Calculating synergistic and antagonistic response of herbicide combinations", Weeds 15, pp 20-22 (1967): EQU EE=x+y-x.multidot.y/100
wherein
If the actual efficacy (E) exceeds the expected (calculated) one (EE), the mixture displays a synergistic effect.